1. Field of the Invention
The present invention relates to a video signal encoding apparatus for encoding a video signal by employing a high efficiency encoding method.
2. Description of the Prior Art
Generally, when recording or transmitting a video signal which has an extremely large quantity of information, it is attempts are made to reduce the quantity of information by high efficiency encoding to such an extent that deterioration of image quality is not visually apparent.
For example, in "AN EXPERIMENTAL DIGITAL VCR WITH NEW DCT-BASED BIT-RATE REDUCTION SYSTEM" by M. Yoneda, et al., IEEE Transactions on Consumer Electronics Vol. 37, No. 3, August 1991, pp. 275-282, such a VCR is disclosed that is capable of recording and reproducing a standard image signal and a high definition image signal by employing orthogonal transformation as a high efficiency encoding method.
This VCR is capable of recording and reproducing different kinds of video signals which differ from each other in the number of pixels, that is, in the sampling frequency, such as a standard picture signal with an aspect ratio of 4:3 and a wide picture signal with an aspect ratio of 16:9. However, such a VCR suffers the following drawbacks.
When the compression ratios in encoding of video signals differing in the number of plxels are the same, the coded data quantities correspond to the respective numbers of pixels. As a result, in the apparatus for recording and reproducing, the recordable time differs, or the recording density in the recording medium must be increased.
On the other hand, when it is attempted to make the coded data quantities of video signals differing in the number of pixels to be the same, the picture quality of the image having a large number of pixels will be deteriorated. Hence, for the image with a large number of pixels, another means for encoding which is distinct from the one use for encoding the standard picture signal is needed, which leads to a complicated circuit composition and recording format.